Abstract: Stray light would reduce the signal to the noise ratio and photometric accuracy of astronomical observations. To ensure the high accuracy photometry of 50 BiN telescopes, the detailed stray light analysis was described. The accurate simulation model of 50 BiN telescopes was built in TracePro and the point source transmittance value of the original optical system was calculated. The vanes inside the primary baffle were designed according to characteristic of the telescopes. Stray light uniformity was analyzed intensively, which played an important role in differential photometry system, stray light uniformity on focal plane was analyzed with MATLAB. These vanes were tested and verified to be effective with MATLAB and TracePro. The analysis results indicate that, at different incident angles, the stray light irradiance standard deviation on CCD focal plane is improved with the help of vanes. For the stray light sources located at the off-axis angle lager than 30, the PSTs of the optical system are approximately 10-10 orders of magnitude. With the help of the vanes inside the primary baffle, the PSTs are declined 3-4 orders. These results show that vanes could improve the ability of stray light suppression and apply to the other telescopes in 50 cm binocular network as well as other astronomical telescopes.